Antenna system

ABSTRACT

The invention relates to an antenna system ( 1 ) comprising several antennae ( 2 ), which can be connected to at least two receivers ( 4, 4 ′) via a combination unit. According to the invention, a signal processing unit ( 5 ) for evaluating the output signals of the receivers ( 4, 4 ′) and a control unit ( 10 ) are provided, by means of which at least one of the antennae can be switched to transmit mode in order to conduct a self-test. These antennae ( 2 ) transmit test signals with a test frequency that is pre-set by a first receiver ( 4 ). Said test signals are fed into at least one other antenna ( 2 ) that, via the combination device ( 3 ), is connected to the second receiver ( 4 ′) whose frequency is tuned to the test frequency. In order to conduct the self-test, the receiving levels of the second receiver ( 4 ′) are recorded as actual values and compared with predetermined set values. This results in the realization of an antenna system in which a function check is conducted with the least possible amount of complexity.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to an antenna system, and, more particularly, the present invention relates to an antenna system having at least two antennae and at least two receivers with self-testing circuitry.

[0003] 2. Description of the Related Technology

[0004] An antenna system is known from DE 196 18 333 A1. This prior antenna system is a component with a mobile broadcast-receiving system and has at least one antenna. The signals received by the antenna are delivered to a receiver made as a superheterodyne receiver. The superheterodyne receiver has a mixer to which one bandpass filter at a time on the input side and the output side is connected. Moreover an oscillator is assigned to the mixer. The bandpass filter upstream of the mixer is used for mirror frequency suppression. The mixer mixes the signal which is at the input with the oscillator signal. The resulting intermediate frequency signal is filtered in the bandpass filter downstream of the mixer and then delivered to a signal processing unit for further processing.

[0005] To check operation of this antenna system, there is a switch that can be switched for control operation in which broadcast signals are received and evaluated, and to a test mode in which a self-test is carried out.

[0006] To carry out the self-test there is a separate transmitting antenna and a circuit arrangement connected to the transmitting antenna.

[0007] The circuit arrangement has a frequency converter which produces a high frequency output signal with which the transmitting antenna is energized.

[0008] The frequency converter is connected to the oscillator of the superheterodyne receiver. Moreover the frequency converter is connected to an intermediate frequency oscillator which is likewise a component of the circuit arrangement. Alternatively to the intermediate frequency oscillator there can be an intermediate frequency limiter which is connected to the output of the superheterodyne receiver.

[0009] The frequency of the high frequency output signal which is generated in the frequency converter is dictated by the intermediate frequency oscillator and the oscillator of the superheterodyne receiver and thus is tuned to the frequency of the superheterodyne receiver.

[0010] The high frequency output signal is capacitively coupled to the antenna of the antenna system via the transmitting antenna.

[0011] The signals at the output of the superheterodyne receiver are detected by a measurement device for carrying out the self-test.

[0012] The disadvantage in this antenna system is that an additional circuit arrangement with a separate transmitting antenna is necessary for carrying out the self-test. This results in undesirably high cost for carrying out the self-test.

SUMMARY OF THE INVENTION

[0013] An object of the invention is to make available an antenna system in which operation can be checked with as little effort as possible.

[0014] This and other objects may be achieved by the antenna system according to the present invention which has several antennae that can be connected to at least two receivers in given combinations via a combination unit. The antenna system furthermore has a signal processing unit for evaluation of the output signals of the receiver and a control unit by means of which at least one of the antennae can be switched to the transmit mode to carry out a self-test. This selected transmit antenna with a test frequency specified via a first receiver sends test signals which are coupled into at least one other antenna which is connected via the combination device to the second receiver with a frequency tuned to the test frequency. The receiving level of the second receiver is detected as an actual value and compared to given setpoints to carry out the self-test.

[0015] The antenna system of the present invention has at least two receivers which in control operation of the antenna system are operated preferably simultaneously. The first receiver is used preferably for preprocessing of the broadcast signals which are received by one antenna and which are instantaneously received and output in the broadcast receiving system. With the other receiver broadcast signals which are received with other antennae are processed to make available additional functions for the broadcast-receiving system.

[0016] These additional functions can be performed, for example, by reception optimization functions, especially Radio Data System (RDS) functions. If a radio transmitter signal is received at a certain frequency with the broadcast receiving system, by means of the second receiver it is checked whether the same content can be received better at other frequencies, i.e. with signals of higher amplitudes or with better signal/noise ratios.

[0017] According to one aspect of the invention, two receivers are used for carrying out the self-test. The self-test and its control are expediently carried out centrally in the control unit.

[0018] To do this, the control unit switches one of the antennae of the antenna system to transmit, this antenna sends test signals with a test frequency which is dictated by the first receiver.

[0019] The antenna which is to be tested at the time is connected to the second receiver with a frequency tuned to the test frequency. To carry out the self-test the reception levels of the test signal are acquired as actual values and compared to given setpoints.

[0020] A major advantage of the antenna system according to the present invention consists in that by using the two receivers to carry out the self-test, separate additional components can be almost completely abandoned. Therefore, the self-test can be carried out with only little additional circuit cost.

[0021] In particular, it is advantageous for the antennae of the antenna system for carrying out the self-test to be switchable to transmit so that there need not be a separate antenna for testing the operation of the antenna system.

[0022] Furthermore, it is advantageous for the test frequency to be tunable via the control unit so that comprehensive and reliable testing of operation is guaranteed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] An antenna system to which the invention is however not limited is explained below with a figure showing an embodiment for the present invention.

[0024]FIG. 1 shows a block diagram of an embodiment of the antenna system according to the present invention.

DETAILED DESCRIPTION

[0025]FIG. 1 shows one embodiment of the antenna system 1 according to the present invention. The antenna system 1 is a component of a mobile broadcast/receiving system which is installed in a motor vehicle (not shown) in this example.

[0026] The antenna system 1 has several antennae 2 which are preferably integrated in a back window of the motor vehicle. The antennae 2 can be made differently and can be used to receive broadcast signals of various frequency ranges. Moreover, individual antennae 2 also can be intended for receiving additional signals which are used for example for remote locking of the motor vehicle.

[0027] The antennae 2 are connected to two receivers 4, 4′ via a combination device 3. Alternatively, more than two receivers 4, 4′ also can be connected. The outputs of the receiver units are routed to a signal processing unit 5 which is formed as an analog integrated circuit or a digital signal processor.

[0028] The combination device 3 is formed using a logic circuit, and by the use of which a given combination of antennae 2 can be switched to each of the receivers 4, 4′. Thus, with the combination device 3 a choice can be made as to which of the antennae 2 are assigned to the individual receivers 4, 4′.

[0029] The receivers 4, 4′ are made as superheterodyne receivers with an essentially identical structure.

[0030] Here each of the receivers 4, 4′ has a mixer 6, 6′ with an oscillator 7, 7′ connected to an input for the mixer 6, 6′. From one output of the combination device 3 a feed line leads via a first bandpass filter 8, 8′ to a second input of the mixer 6, 6′. The output of the mixer 6, 6′ is routed via a second bandpass filter 9, 9′ to the signal processing unit 5.

[0031] The first bandpass filter 8, 8′ is tuned to the frequency of the broadcast signals received with the antennae 2. The filtered output signal of the combination device 3 and the signal of the oscillator 7, 7′ are mixed in the mixer 6, 6′, so that a lower frequency intermediate frequency signal is generated from the high frequency broadcast signal. The intermediate frequency signal corresponds to the difference of the frequencies of the broadcast signal and of the oscillator 7, 7′. The intermediate frequency signal is then filtered in the second bandpass filter 9, 9′ which is permanently set to the intermediate frequency. The output signal of the respective receiver 4, 4′ obtained in this way is further processed in the signal processing unit 5.

[0032] The combination device 3 is controlled via the control unit 10 which is preferably formed using a microcontroller. The oscillators 7, 7′ of the receivers 4, 4′ are controlled by the control unit 10.

[0033] A self-test is run according to one aspect for the invention to check serviceability. The self-test preferably is carried out during given time intervals which interrupt the control operation of the antenna system 1. Typically one such self-test takes place after completed assembly of the motor vehicle, during parking times of the motor vehicle in a shop, and when the broadcast-receiving system is turned on. Execution and control of the self-test takes place centrally via the control unit 10.

[0034] To control the self-test, there especially is a switch 11 which is connected to the control unit 10. The switch 11 is located on a feed line which connects the oscillator 7 of the first receiver 4 to the combination device 3.

[0035] To carry out the self-test, the output of the second receiver 4′ has a level measuring device 12. The level measuring device 12 is connected to the control unit 10 so that the reception level detected with the level measurement device 12 is fed into the control unit 10 for further evaluation.

[0036] During the control operation of the antenna system 1 broadcast signals in particular are received with the antennae 2. They are the broadcast signals of the radio transmitter which is set at the time in the broadcast/receiving system.

[0037] At least one other antenna 2 is switched to the other receiver 4′ or 4. In this receiver 4′ or 4 the broadcast signals are readily received and evaluated to prepare additional functions for the broadcast/receiver system. These additional functions can be formed especially by reception optimization functions, for example, the Radio Data System (RDS) function.

[0038] This function is used to optimize reception of a certain radio transmitter in the broadcast-reception system.

[0039] While the broadcast signals of the radio transmitter which have been received in the first receiver 4 or 4′ are reproduced via the broadcast-reception system; in the background broadcast signals having the same content which however are sent with different frequencies and which are received with the second receiver 4′ or 4 are evaluated. Then in the signal processing unit 5 a check is made as to what frequency broadcast signals of the same content are optimally received, i.e. for which frequency the highest signal amplitude and/or the best signal/noise ratio is obtained. Next the broadcast signals with the optimum frequency for reproduction can be selected via the signal processing unit 5.

[0040] Control operation is interrupted at set times via the control unit 10 so that the antenna system 1 is switched into a test mode for executing the self-test. The duration of the self-test is dictated via the control unit 10.

[0041] At the start of the self-test the switch 11 is closed via the control unit 10. Moreover, the control unit 10 inputs a control command into the combination device 3. One of the antennae 2 is switched to transmit by the control command from the combination device 3. The antenna 2 operated in the transmit mode is connected by the closed switch 11 to the oscillator 7 of the first receiver 4. Thus the antenna 2 operated in the transmit mode sends test signals with a test frequency which is given by the oscillator 7 of the first receiver 4.

[0042] Feasibly the antenna 2 operated in transmit mode is not one of the antennae 2 of the antenna system 1 which are being used for current reception of broadcast signals.

[0043] Furthermore, selection of the antennae 2 which are to be checked during the self-test and which are preferably connected individually in succession via the combination device 3 to the second receiver 4′ takes place using the control unit 10.

[0044] The test signals transmitted by the antenna 2 operated in the transmit mode are coupled to the antenna 2 which is to be checked and which is connected to the second receiver 4′. The test signals received by this antenna 2 are evaluated in the second receiver 4′.

[0045] The frequency of the second receiver 4′ is tuned to the test frequency which is generated in the oscillator 7 of the first receiver 4. If for example the test frequency is 100 MHz, the bandpass filter 8′ of the second receiver 4 is tuned accordingly to this test frequency. In particular, the oscillator 7′ of the second receiver 4′ is tuned to the test frequency. In this example its frequency is 110.7 MHz so that the intermediate frequency signal at the output of the mixer 6′ is 10.7 MHz, the downstream bandpass filter 9′ being tuned to this intermediate frequency.

[0046] Expediently the test frequency, i.e. the frequency of the oscillator 7 of the first receiver 4, can be tuned via the control unit 10. Accordingly, the frequency of the oscillator 7′ of the second receiver 4′ also is changed.

[0047] The arrangement formed in this way for running the self-test thus has a two-channel structure. The first receiver 4 with the antenna 2 operated in the transmit mode forms a first channel, while the second receiver 4′ with the antenna 2 to be checked forms the second channel.

[0048] The test signals are coupled into the antenna 2 to be checked by the transmitting antenna. The corresponding reception levels on the second receiver 4′ are detected in the level measurement device 12 and are read into the control unit 10.

[0049] In doing so the reception levels detected with the level measurement device 12 provide actual values which are compared in the control unit 10 to the setpoints which are stored and specified there. In addition or alternatively, the signals provided to evaluate the reception quality and which are obtained from the signal processing unit 5 as the output signals of the second receiver 4′ can be read as actual values into the control unit 10 and can be compared there in turn with suitable setpoints.

[0050] In general, the comparison of the current values to the setpoints in the control unit 10 provides a measure of quality for the signals which are being received with the antenna 2 which is to be checked. Preferably comparison of actual values to the setpoints takes place using the tolerance ranges given in the control unit 10. Relatively fault-free operation of the antenna system 1 exists when the actual values agree with the setpoints within the respective tolerance ranges.

[0051] In testing of operation, preferably all the antennae 2 required for reception are tested. To ensure that testing of operation is as reliable and comprehensive as possible, the test frequency within a given frequency range is changed during the self-test.

[0052] When the self-test has been completed by the control unit 10, the switch 11 is opened and the antenna which is operated during the self-test in the transmit mode is switched again to the reception mode.

Reference Number List

[0053] (1) antenna system (2) antenna (3) combination device (4) receiver (4′) receiver (5) signal processing unit (6) mixer (6′) mixer (7) oscillator (7′) oscillator (8) bandpass filter (8′) bandpass filter (9) bandpass filter (9′) bandpass filter (10) control unit (11) switch (12) level measurement means 

1. Antenna system (1) with several antennae (2) which can be connected to at least two receivers (4, 4′) in given combinations via a combination unit, with a signal processing unit (5) for evaluation of the output signals of the receivers (4, 4′) and with a control unit (10), by means of which at least one of the antennae (2) can be switched to transmitting operation to carry out a self-test, this antenna (2) with a test frequency dictated via a first receiver (4) sending test signals which are coupled into at least one other antenna (2) which is connected via the combination device (3) to the second receiver (4′) with a frequency tuned to the test frequency, and the reception levels of the second receiver (4′) being detected as actual values and being compared to given setpoints to carry out the self-test.
 2. Antenna system as claimed in claim 1, wherein the receivers (4, 4′) are each formed by a superheterodyne receiver, each of the receivers (4, 4′) having a mixer (6, 6′) to which an oscillator (7, 7′) is connected, and there being one bandpass filter (8, 8′, 9, 9′) on the input side and the output side of the mixer (6, 6′).
 3. Antenna system as claimed in claim 2, wherein the test frequency for the antenna (2) operated in the transmit mode during the self-test is generated by the oscillator (7, 7′) of the first receiver (4).
 4. Antenna system as claimed in claim 3, wherein the oscillator (7, 7′) of the first receiver (4) is connected to the combination device (3) via a feed line which has a switch (11), and the switch (11) can be actuated via the control unit (10).
 5. Antenna system as claimed in claim 4, wherein the switch (11) is closed only during the self-test.
 6. Antenna system as claimed in one of claims 2 to 5, wherein a level measurement means (12) for determining the actual values is connected downstream of the bandpass at the output of the second receiver (4′).
 7. Antenna system as claimed in claim 6, wherein the level measurement means (12) is connected to the control unit (10) in which the actual values are compared to the setpoints stored in the control unit (10).
 8. Antenna system as claimed in one of claims 6 or 7, wherein the signals which evaluate the reception quality and which form actual values from the signal processing unit (5) are read into the control unit (10) for comparison with the setpoints stored there.
 9. Antenna system as claimed in one of claims 2 to 8, wherein the oscillator (7, 7′) of the second receiver (4′) is tuned to the test frequency during the self-test.
 10. Antenna system as claimed in one of claims 2 to 9, wherein the frequencies of the oscillators (7, 7′) can be set via the control unit (10).
 11. Antenna system as claimed in claim 10, wherein the frequencies of the oscillators (7, 7′) are changed in a given frequency range for carrying out the self-test.
 12. Antenna system as claimed in one of claims 1 to 11, wherein the control unit (10) is formed by the microcontroller.
 13. Antenna system as claimed in one of claims 1 to 12, wherein it is integrated in a motor vehicle as a component of a broadcast receiving system.
 14. Antenna system as claimed in claim 13, wherein the antennae are integrated into the rear window of the motor vehicle.
 15. Antenna system as claimed in claim 13 or 14, wherein during its control operation by means of a receiver (4) broadcast signals receiving [sic] from a combination or selection of antennae (2) and sent at a first frequency are processed for reproduction in the broadcast receiving system, and wherein by means of another receiver (4′) broadcast signals received by another antenna (2) and sent at a second frequency are processed and are further processed to make available additional functions in the broadcast receiving system in the signal processing unit (5).
 16. Antenna system as claimed in claim 15, wherein the additional functions are formed by the reception optimization functions. 